Year	Percent
1960-01-01	30.7018275365962
1961-01-01	30.8248247650448
1962-01-01	31.6650468212131
1963-01-01	32.9178554961588
1964-01-01	33.8352062995020
1965-01-01	34.2823167772263
1966-01-01	34.1600588879973
1967-01-01	34.0327622952624
1968-01-01	34.0144490982626
1969-01-01	34.4132590283678
1970-01-01	34.5728053066407
1971-01-01	34.9076068295922
1972-01-01	35.4694784671490
1973-01-01	35.1989228370207
1974-01-01	36.1577817804213
1975-01-01	36.7737664897953
1976-01-01	36.8524311762588
1977-01-01	36.6769872517306
1978-01-01	36.4273799027986
1979-01-01	36.3770983022780
1980-01-01	36.5137202218387
1981-01-01	36.4892653243630
1982-01-01	36.4336129561161
1983-01-01	35.9509477195943
1984-01-01	36.2678999399463
1985-01-01	36.6520672409780
1986-01-01	36.8503365503151
1987-01-01	37.0759311247141
1988-01-01	37.0864786978926
1989-01-01	36.8279065736976
1990-01-01	36.4265461471281
1991-01-01	35.9377305140307
1992-01-01	35.8688374446632
1993-01-01	36.1172017876412
1994-01-01	36.3257765391677
1995-01-01	36.5273028386772
1996-01-01	36.4659588331901
1997-01-01	36.2729705993759
1998-01-01	36.6186414938234
1999-01-01	37.0445475388739
2000-01-01	37.4834307958136
2001-01-01	37.9261135987635
2002-01-01	38.7338269691443
2003-01-01	39.1270938104580
2004-01-01	39.4942500185162
2005-01-01	39.5197167033092
2006-01-01	39.5404416443644
2007-01-01	39.5600381055788
2008-01-01	39.7703656467152
2009-01-01	40.0685322028211
2010-01-01	40.2801226090453
2011-01-01	40.6519481779271
2012-01-01	40.8951404015640
2013-01-01	40.6206248923249
2014-01-01	40.4782819669271
2015-01-01	40.3404974719951
2016-01-01	39.9078995986495
2017-01-01	39.4666379714566